1. Field of the Invention
The invention relates to a longitudinal drive shaft for transferring a torque in motor vehicles, consisting of two or more shaft sections and a joint, in which the shaft sections are connected by an intermediate shaft or a journal.
2. The Prior Art
Such longitudinal drive shafts are generally known and serve to transfer a torque and are configured so that in a frontal collision or a crash in the longitudinal direction of the vehicle, the longitudinal shaft shortens in the axial direction, in order to prevent bending out and penetration into the interior of the vehicle. At the same time, injuries to passengers are precluded to the greatest possible extent. A longitudinal drive shaft for motor vehicles of the type described above has become known from German Patent No. DE 43 44 177 C1.
This longitudinal drive shaft for motor vehicles has an intermediate joint that is configured as an axially displaceable ball rotary joint and consists of at least one outer joint part having first ball raceways that run longitudinally, an inner joint part having second ball raceways that run longitudinally, and balls that transfer torque and are each guided in first and second ball raceways that lie radially opposite one another. In this connection, the outer joint part is rigidly connected with the tubular shaft, and the inner joint part is rigidly connected with the shaft journal. The inside diameters of the outer joint part or of the subsequent tubular shaft, subsequent to the free space taken up by the inner joint part in operation, in the case of pushing movements, in the direction towards the tubular shaft, are configured to be smaller than the outside diameter of the inner joint part.
With this configuration, the result is supposed to be achieved that in case of a “crash,” energy is reduced or absorbed by the longitudinal shaft, by means of friction and widening of the parts of the drive shaft that are displaced into one another. It is a disadvantage, however, that bending out of the longitudinal drive shaft can take place as a result of forces acting during the crash.
Another solution of this type is described in German Patent No. DE 42 24 201 C2, with which a longitudinal shaft in the drive train of a motor vehicle is configured so that the other parts of the longitudinal shaft remain undamaged by means of a connection between the inner joint part and the shaft journal, which connection is releasable at a predetermined axial force in the drive train. For this purpose, axial stopping means are provided for the inner joint part, in the outer joint part, on which means the inner joint part is supposed to support itself when the connection between the inner joint part and the shaft journal is released, and the shaft journal is subsequently pushed through the inner joint part.
In the same way, support is supposed to take place by an introduction cone in the outer joint part, or in a bottom part that follows it and is connected with the outer joint part. It is emphasized as being particularly advantageous that a targeted axial force, deviating from zero in a positive manner, having controlled energy absorption, can be adjusted by the means for absorbing friction work or deformation work when the shaft journal is axially pushed through the inner joint part and into the introduction cone.
This solution also has the disadvantage that in the case of an accident, this longitudinal drive shaft can also bend out and penetrate into the passenger space, which can lead to injuries to the persons situated in the passenger space. Furthermore, the maximal length of the crash path is very disadvantageous in the case of this variant, since the shaft journal cannot be selected to have simply any desired length, because in the case of a shaft journal having a greater length, bending-critical speeds of the rotation of the longitudinal shaft occur, which also have a disadvantageous effect on the stability system of a longitudinal shaft configured in such a manner.
Furthermore, German Patent No. DE 199 43 880 C1 describes a drive arrangement with a longitudinal drive shaft and an intermediate bearing, which are used in motor vehicles.
This longitudinal drive shaft consists of a first shaft section having a first joint, a second shaft section having a second joint, and a third joint in the form of a homokinetic fixed joint, which connects the first shaft section and the second shaft section, and comprises the intermediate bearing, which is assigned to the first shaft section, and adjacent to the fixed homokinetic joint, a roller bearing. With this drive arrangement, the smallest inside diameters of the outer joint part, of the second shaft pipe, of the outer joint part of the joint, and of the shaft pipe that belongs to the second shaft section, are greater than the greatest outside diameters of the first shaft section and of the roller bearing of the intermediate bearing.
With this arrangement, it is supposed to be possible for the two shaft sections to move into one another in the manner of a telescope, essentially without force, if the maximally permissible displacement path of the first joint and of the second joint, in the axial direction, is exceeded, for example due to a frontal impact of the vehicle.
By means of the different dimensions of the functional parts of the drive arrangement, in order to be able to telescope them, it is guaranteed that these parts will be pushed into one another, but significant force effects are required to initiate this process of telescoping, and again it cannot be precluded that the longitudinal drive shaft bends out.